1. Field of the Invention
This invention relates to a process for the production of ceramic substrates for thin layer circuits in which a cast compound is produced, which may be transformed into a ceramic body by means of a sintering process, the compound being poured out in the form of a coating on a base to air dry and form a "green" substrate layer from which the required shape may be subsequently punched out and sintered.
2. Description of the Prior Art
The marked insulating properties of ceramic substrates make them a preferred material for the production of substrates for electronic circuits. Thin layer elements make particular requirements on the surface quality of the substrates since the layer thicknesses on such a substrate are in the region of from 100 to several 1000 A. If the roughness of the surface of a substrate is too great, no complete layers of this thickness are produced.
Substrates suitable for thin layer circuits are produced in a known manner, for example, in accordance with the German patent application 1,771,216, which has been laid open to public inspection. The object of this known process is to provide a substrate compound which remains particularly homogenous and pore-free during the sintering process. It is proposed, in particular, that alumina be used for this purpose, the granule size distribution of the material being staggered over a wide range. In order to avoid distortion during the sintering of the substrate, the latter must be weighted down with pre-sintered molded components during the sintering process. Heavy loading with molded components prevents the substrates from shrinking during the sintering process. Cracks are, however formed. On the other hand, a lighter load with molded components during sintering is not sufficient to prevent deformation and buckling of the substrates.